In electrophotographic copiers, sheets of paper are heated and pressurized by fixing units in order to fix toner images formed on the sheets of paper. A large amount of power is required to heat the fixing units. The power consumed in such an image forming apparatus tends to increase in response to a request to, for example, increase the processing speed. At the same time, an upper limit is set for the current value capable of being acquired from a single outlet of a commercial power supply. For example, the current value is set within 100V/15 A in Japan. Accordingly, it is necessary to set the power consumed in the image forming apparatus to a value lower than the power capable of being supplied from the commercial power supply.
To this end, the total amount of current consumption in the image forming apparatus is measured to control the power to be supplied to the fixing unit in accordance with the result of the measurement (for example, refer to Japanese Patent Laid-Open No. 2008-292988).
However, when an apparatus is operated in a state in which the total amount of current consumption of the apparatus is close to a current limit value, a state in which the power exceeds the limit value and a state in which the power is lower than the limit value are repeated to cause many ripples in the fixing power. Accordingly, it is not possible to efficiently use the power and a moment at which the total amount of current consumption exceeds an upper threshold value occurs.
One disclosed aspect of the embodiments provides a technology to keep the maximum productivity of an image forming operation by preventing the current consumption from exceeding a limit value and efficiently using the power within the limit.